For Educational Use Only · Not a Substitute for Institutional Protocols
HF
HFNC IQ
High-Flow Nasal Cannula · ICU Education
ICU IQ Suite
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High-Flow Nasal Cannula

Heated, humidified oxygen at high flow — the escalation step between conventional O₂ and non-invasive ventilation.

High-flow nasal cannula (HFNC) delivers heated, humidified oxygen at flow rates up to 60–70 L/min through wide-bore nasal prongs, with FiO₂ set independently of flow. It sits on the respiratory-support ladder between conventional oxygen and non-invasive ventilation.

Four mechanisms of benefit

  • Anatomical dead-space washout — high flow flushes CO₂-rich gas from the upper airway, improving alveolar ventilation efficiency.8,9
  • Low-level PEEP effect — flow generates a few cmH₂O of positive airway pressure (flow-dependent, greatest with the mouth closed).8
  • Reduced work of breathing — meeting or exceeding the patient's inspiratory demand lowers respiratory effort and inspiratory resistance.8,9
  • Optimal humidification — gas conditioned to ~37 °C / 44 mg/L preserves mucociliary function and comfort, enabling tolerance for long periods.9

Where HFNC fits

Conventional O₂ → HFNC → non-invasive ventilation → intubation. HFNC is a strong first-line support for hypoxemic respiratory failure, but it is not a ceiling: recognizing failure early and not delaying intubation is the central safety principle.

The evidence, honestly. The 2015 FLORALI trial showed a 90-day mortality signal favoring HFNC over standard oxygen and NIV, though intubation rates did not differ significantly.1 That mortality benefit has not been consistently reproduced since. Current guidelines recommend HFNC over conventional oxygen in hypoxemic failure largely on intubation, comfort, and physiologic grounds — not a settled mortality benefit.6,7
When to escalate, not persist. A failing patient kept on HFNC too long has worse outcomes once finally intubated. Use the ROX index and clinical trajectory (see Calculators) rather than waiting for a crash.5,13
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Education Modules

Core lessons. Each clinical claim is keyed to a source in the Sources tab.

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Weaning Protocol Navigator

Enter the current state; get the single next protocol action — from high flow all the way to room air.

Your facility's order governs. This encodes a representative RN-driven oxygen-titration protocol. Device minimum flow varies by machine — confirm against your unit's order and equipment. Not a substitute for clinical judgment.
The full pathway

The two linked orders carry a patient the whole way to room air:

  1. HFNC: wean FiO₂ in 5% steps to a 40% floor, then wean flow in 10 L/min steps to device minimum.A
  2. Hold at 40% and device-minimum flow for 24 h, then step down to nasal cannula at 5 L/min.A
  3. Nasal cannula: routine wean 1 L/min every 30–60 min; once daily attempt to wean off (1–2 L/min per ≥30 min) while SpO₂ holds.B
  4. Discontinue oximetry once off oxygen 24 h with SpO₂ at goal and improved work of breathing.A
Why FiO₂ before flow? FiO₂ addresses oxygenation reserve; flow delivers the PEEP, dead-space washout, and work-of-breathing support. Weaning FiO₂ to a safe conventional level first preserves the physiologic support longest.8,9
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Patient Simulator

Titrate a virtual patient over time. Wean the responders to room air — and recognize the ones who need the tube before they crash.

Teaching model, not a monitor. A simplified physiology engine for practicing titration and failure recognition. The numbers are illustrative, not a validated clinical predictor.
Choose a scenario
Elapsed: 0h 00m
FiO₂100%
Flow50 L/min
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Calculators

ROX index for failure prediction, and the SpO₂/FiO₂ ratio.

ROX Index — HFNC failure prediction
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Enter SpO₂, FiO₂, and respiratory rate. ROX = (SpO₂/FiO₂) ÷ RR.
Roca et al: ROX ≥ 4.88 at 2, 6, and 12 h predicts lower intubation risk; < 3.85 flags high failure risk; the zone between warrants close reassessment. Accuracy rises the longer the patient is on HFNC.5
SpO₂ / FiO₂ ratio
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A non-invasive oxygenation index. S/F = SpO₂ ÷ FiO₂ (fraction).
S/F is a rough, non-invasive surrogate for P/F and should not replace an ABG-based assessment when precision matters. Keep SpO₂ in the 88–96% range for the surrogate to behave sensibly.
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Respiratory Support Ladder

Where HFNC sits, and the failure trajectory to watch.

HFNC bridges conventional oxygen and non-invasive ventilation. Moving up the ladder is a clinical decision, not a fixed FiO₂ threshold — but a rising FiO₂ requirement, climbing respiratory rate, and a falling ROX are the signals that the current rung is failing.

The failure trajectory: a ROX that fails to rise — or falls — across the 2 h, 6 h, and 12 h reassessment windows is the early warning to escalate rather than persist.5,13

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Knowledge Check

Clinical scenarios with feedback.

Question 1
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Sources

Load-bearing references (1–10) verified live; protocol keys A–B are institutional orders.

Verification note. References 1–10 were confirmed against PubMed / publisher records. The weaning cut-points reflect a representative facility oxygen-titration order and are not RCT-validated numbers — confirm against your own order text and have clinical content reviewed before institutional use.
HFNC IQ v1.3  ·  ICU IQ Suite  ·  For Educational Use Only
Not a substitute for clinical judgment or institutional protocols.